
By Adda Bjarnadottir
Docosahexaenoic acid (DHA) is one of the most important omega-3 fatty acids. Like most omega-3 fats, it's linked with many health benefits.
It is a part of every cell in your body, plays a vital role in your brain and is absolutely crucial during pregnancy and infancy. Since your body can't produce it in adequate amounts, it's essential to get it from your diet.
Docosahexaenoic acid (DHA) is one of the most important omega-3 fatty acids.Photo credit: Shutterstock
This article explains everything you need to know about DHA.
What is DHA (Docosahexaenoic Acid)?
Docosahexaenoic acid (DHA) is a long-chain omega-3 fatty acid.
It's 22 carbons long, has 6 double bonds and is mainly found in seafood, such as fish, shellfish, fish oils and some types of algae.
It's a component of every cell in your body and a vital structural component of your skin, eyes and brain (1, 2, 3, 4).
In fact, DHA makes up more than 90 percent of the omega-3 fatty acids in your brain and up to 25 percent of its total fat content (3, 5).
Technically, it can be synthesized from another plant-based omega-3 fatty acid called alpha-linolenic acid (ALA). However, this process is very inefficient and only 0.1–0.5 percent of ALA is converted into DHA in your body (6, 7, 8, 9, 10).
What's more, the conversion also relies on adequate levels of other vitamins and minerals, as well as the amount of omega-6 fatty acids in your diet (11, 12, 13).
Because your body can't make DHA in significant amounts, you need to get it from your diet or supplements.
Bottom Line: DHA is an omega-3 fatty acid that is vital for your skin, eyes and brain. Your body can't produce it in adequate amounts, so you need to get it from your diet.
How Does it Work?
DHA is an unsaturated fatty acid with 6 double bonds. This means it's very flexible.
It's mainly located in cell membranes, where it makes the membranes and gaps between cells more fluid (14).
This makes it easier for cells to send and receive electrical signals, which is their way of communicating (15).
Therefore, adequate levels of DHA seem to make it easier, quicker and more efficient for cells to communicate.
Having low levels in your brain or eyes may slow the signaling between cells, resulting in poor eyesight or altered brain function.
Bottom Line: DHA makes the membranes and gaps between cells more fluid, making it easier for cells to communicate.
Top Food Sources of DHA
DHA is mainly found in seafood, such as fish, shellfish and algae.
Several types of fish are excellent sources, providing up to several grams per serving (16).
These include:
- Mackerel.
- Herring.
- Sardines.
- Caviar.
Some fish oils, such as cod liver oil, can provide as much as 1 gram of DHA in one tablespoon (10–15 ml) (17).
Just keep in mind that fish oils may also be high in vitamin A, which can be harmful in large amounts.
DHA may also be present in small amounts in meat and dairy from grass-fed animals, as well as omega-3 enriched or pastured eggs.
However, it may be hard to get enough from your diet alone. So if you don't regularly eat the foods mentioned above, taking a supplement may be a good idea.
Bottom Line: DHA is mostly found in fatty fish, shellfish, fish oils and algae. Grass-fed meat, dairy and omega-3 enriched eggs may also contain small amounts.
Effects on the Brain
DHA is the most abundant omega-3 in your brain and plays a critical role in its development and function.
Brain levels of other omega-3 fatty acids, such as EPA, are typically 250–300 times lower (3, 4,18).
It Plays a Major Role in Brain Development
DHA is extremely important for brain tissue growth and function, especially during development and infancy (19, 20).
It needs to accumulate in the central nervous system in order for the eyes and brain to develop normally (3, 4).
DHA intake during the third trimester of pregnancy determines the baby's levels, with the greatest accumulation occurring in the brain during the first few months of life (3).
DHA is mainly found in the gray matter of the brain and the frontal lobes are particularly dependent on it during development (21, 22).
These parts of the brain are responsible for processing information, memories and emotions. They are also important for sustained attention, planning and problem solving, as well as social, emotional and behavioral development (4, 5, 23).
In animals, decreased DHA in a developing brain leads to a reduced amount of new nerve cells and altered nerve function. It also impairs learning and eyesight (24).
In humans, DHA deficiency in early life has been associated with learning disabilities, ADHD, aggressive hostility and several other disorders (25, 26).
Furthermore, studies have linked low levels in the mother to an increased risk of poor visual and neural development in the child (3, 24, 27).
Studies have shown that babies of mothers who consumed 200 mg per day from the 24th week of pregnancy until delivery had improvements in vision and problem solving (3, 28).
Bottom Line: DHA is essential for brain and eye development. A deficiency in early life is linked to learning disabilities, ADHD and other disorders.
It May Have Benefits for the Aging Brain
DHA is also critical for healthy brain aging (29, 30, 31, 32).
There are many factors that come naturally with brain aging, such as oxidative stress, altered energy metabolism and DNA damage (33, 34, 35).
The structure of the brain also changes, which reduces its size, weight and fat content (36, 37).
Interestingly, many of these changes are also seen when DHA levels decrease.
This includes altered membrane properties, decreased performance in memory tasks, altered enzyme activity and altered neuron function (38, 39, 40, 41, 42).
Taking a supplement may help. DHA supplements have been linked to significant improvements in memory, learning and verbal fluency for those with mild memory complaints (43, 44, 45, 46, 47, 48).
Bottom Line: A DHA deficiency may disrupt brain function. Supplements may improve memory, learning and verbal fluency for certain people.
Low Levels Are Linked to Brain Diseases
Alzheimer's disease is the most common form of dementia in older people.
It affects about 4.4 percent of adults over 65 and impacts brain function, mood and behavior (49, 50).
Changes in episodic memory are among the earliest signs of brain changes in older adults. This refers to difficulty recalling events that occurred at a specific time and place (44, 51, 52, 53).
Interestingly, Alzheimer's disease patients have been shown to have lower amounts of DHA in the brain and liver, while EPA and DPA levels are elevated (54, 55).
Studies show that higher blood DHA levels are linked to a reduced risk of developing dementia and Alzheimer's (56).
Bottom Line: Low DHA levels are linked to an increased risk of developing memory complaints, dementia and Alzheimer's disease.
Effects on Eyes and Vision
DHA is a very important membrane component in the eye. It helps activate a protein called rhodopsin, a membrane protein in the rods of the eye.
Rhodopsin helps your brain receive images from your eyes by altering permeability, fluidity, thickness and other properties inside the eye (57, 58).
A DHA deficiency can cause vision problems, especially in children (3, 24, 27).
Therefore, baby formula is now generally fortified with it, which is an effective way to help prevent vision impairment in babies (59, 60).
Bottom Line: DHA is important for vision and various functions inside the eye. A deficiency may cause vision problems in children.
Effects on Heart Health
Omega-3 fatty acids have generally been linked to a reduced risk of heart disease.
Low levels are associated with an increased risk of heart disease and death and some (but not all) supplement studies have shown that omega-3s reduce the risk (61, 62, 63, 64).
This applies especially to the long-chain omega-3 fatty acids found in fatty fish and fish oils, such as EPA and DHA.
Their intake can improve many risk factors for heart disease, including:
- Blood triglycerides: Long-chain omega-3 fatty acids may reduce blood triglycerides by up to 30 percent (65, 66, 67, 68, 69).
- Blood pressure: The omega-3 fatty acids in fish oils and fatty fish may reduce blood pressure in people with high blood pressure (70, 71, 72).
- Cholesterol levels: Fish oils and omega-3s may lower total cholesterol and increase HDL cholesterol in people with high cholesterol levels (73, 74, 75).
- Endothelial function: DHA may protect against endothelial dysfunction, which is a leading driver of heart disease (76, 77, 78, 79).
Bottom Line: DHA may reduce the risk of heart disease by lowering blood triglycerides and blood pressure, improving cholesterol levels and protecting against endothelial dysfunction.
Other Health Benefits
DHA may also protect against the development of other diseases, including:
- Arthritis: It reduces inflammation in the body and may alleviate the pain and inflammation in the joints of people with arthritis (80, 81).
- Cancer: It may make it more difficult for cancer cells to survive. It may also cause them to die via programmed cell death (82, 83, 84, 85, 86).
- Asthma: It may reduce asthma symptoms, possibly by blocking mucus secretion and reducing blood pressure (87, 88, 89).
Bottom Line: DHA may also help with conditions like arthritis and asthma, as well as prevent the growth of cancer cells.
DHA is Especially Important During Pregnancy, Lactation and Childhood
DHA is critical during the last months of pregnancy and early in a baby's life.
Babies up to the age of two have a greater need for it than older children and adults (3, 90, 91).
Their brains are growing rapidly and need high amounts of DHA to form vital cell membrane structures in the brain and eyes (3, 92).
Therefore, DHA intake can dramatically affect brain development (27, 93).
Animal studies show that DHA-deficient diets during pregnancy, lactation and weaning limit the supply to the infant's brain to only about 20 percent of normal levels (94).
Deficiency is associated with changes in brain function, including learning disabilities, changes in gene expression and impaired vision (24).
Bottom Line: During pregnancy and early life, DHA is vital for the formation of structures in the brain and eyes.
How Much DHA Do You Need?
Most guidelines for healthy adults recommend at least 250–500 mg of combined EPA and DHA per day (95, 96, 97, 98, 99, 100).
Studies show the average DHA intake is closer to 100 mg per day (101, 102, 103).
Children up to the age of two may need 4.5–5.5 mg/lb (10–12 mg/kg) of body weight, while older children may need up to 250 mg per day (104).
Pregnant or breastfeeding mothers are advised to get at least 200 mg of DHA or 300–900 mg of combined EPA and DHA, per day (93, 97).
People with mild memory complaints or cognitive impairments may benefit from 500–1,700 mg of DHA per day to improve brain function (43, 44, 45, 46, 47, 48).
Vegetarians and vegans are often lacking in DHA and should consider taking microalgae supplements that contain DHA (11, 105).
DHA supplements are usually safe. However, taking more than 2 grams a day does not have any added benefits and is not recommended (106, 107, 108).
Interestingly, curcumin—the active compound in turmeric—may enhance DHA absorption in the body. It's linked with many health benefits and animal studies have shown that it may boost DHA levels in the brain (109, 110).
Therefore, curcumin may be helpful when supplementing with DHA.
Bottom Line: Adults should get 250–500 mg of combined EPA and DHA daily, while children should get 4.5–5.5 mg/lb (10–12 mg/kg) of body weight.
Considerations and Adverse Effects
DHA supplements are usually well tolerated, even in large doses.
However, omega-3s are generally anti-inflammatory and may thin the blood (111).
Consequently, too much omega-3 may cause blood thinning or excessive bleeding.
If you are planning surgery, you should stop supplementing with omega-3 fatty acids a week or two beforehand.
Also make sure to speak with a doctor before taking omega-3s if you have a blood clotting disorder or take blood thinning medication.
Bottom Line: Like other omega-3 fatty acids, DHA may cause blood thinning. You should avoid taking omega-3 supplements 1-2 weeks before surgery.
Take Home Message
DHA is a vital part of every cell in your body, especially the cells in your brain and eyes.
It's also an essential part of brain development and function. What's more, it may affect the speed and quality of communication between nerve cells.
Furthermore, DHA is important for your eyes and it may reduce many risk factors for developing heart disease.
If you suspect you're not getting enough in your diet, consider taking an omega-3 supplement. It is one of the few supplements that may actually be worth the money.
This article was reposted from our media associate Authority Nutrition.
YOU MIGHT ALSO LIKE
The Unsung Superfood: 4 Reasons to Love Parsley
10 'Low-Fat' Foods That Should Not Be Part of a Healthy Diet
In 2010, world leaders agreed to 20 targets to protect Earth's biodiversity over the next decade. By 2020, none of them had been met. Now, the question is whether the world can do any better once new targets are set during the meeting of the UN Convention on Biodiversity in Kunming, China later this year.
- Ocean Scientists Create Global Network to Help Save Biodiversity ... ›
- 5 Reasons Why Biodiversity Matters - EcoWatch ›
- 26 Organizations Working to Conserve Seed Biodiversity - EcoWatch ›
- The Top 10 Ocean Biodiversity Hotspots to Protect - EcoWatch ›
- New Platform Shows How to Protect Biodiversity and Save Planet ... ›
- These Scientists Are Listening to the Borneo Rainforest to Protect ... ›
EcoWatch Daily Newsletter
By Andrew Rosenberg
The first 24 hours of the administration of President Joe Biden were filled not only with ceremony, but also with real action. Executive orders and other directives were quickly signed. More actions have followed. All consequential. Many provide a basis for not just undoing actions of the previous administration, but also making real advances in public policy to protect public health, safety, and the environment.
- Here Are Biden's Day One Actions on Climate and Environment ... ›
- UCS Offers Science Advice for Biden Administration - EcoWatch ›
Trending
A first-of-its-kind study has examined the satellite record to see how the climate crisis is impacting all of the planet's ice.
- 'Ghost Forests' Are an Eerie Sign of Sea-Level Rise - EcoWatch ›
- Sea-Level Rise Takes Business Toll in North Carolina's Outer Banks ... ›
- Sea Level Rise Is Locked in Even If We Meet Paris Agreement ... ›
A Healthy Microbiome Builds a Strong Immune System That Could Help Defeat COVID-19
By Ana Maldonado-Contreras
Takeaways
- Your gut is home to trillions of bacteria that are vital for keeping you healthy.
- Some of these microbes help to regulate the immune system.
- New research, which has not yet been peer-reviewed, shows the presence of certain bacteria in the gut may reveal which people are more vulnerable to a more severe case of COVID-19.
You may not know it, but you have an army of microbes living inside of you that are essential for fighting off threats, including the virus that causes COVID-19.
How Do Resident Bacteria Keep You Healthy?
<p>Our immune defense is part of a complex biological response against harmful pathogens, such as viruses or bacteria. However, because our bodies are inhabited by trillions of mostly beneficial bacteria, virus and fungi, activation of our immune response is tightly regulated to distinguish between harmful and helpful microbes.</p><p>Our bacteria are spectacular companions diligently helping prime our immune system defenses to combat infections. A seminal study found that mice treated with antibiotics that eliminate bacteria in the gut exhibited an impaired immune response. These animals had low counts of virus-fighting white blood cells, weak antibody responses and poor production of a protein that is vital for <a href="https://doi.org/10.1073/pnas.1019378108" target="_blank">combating viral infection and modulating the immune response</a>.</p><p><a href="https://doi.org/10.1371/journal.pone.0184976" target="_blank" rel="noopener noreferrer">In another study</a>, mice were fed <em>Lactobacillus</em> bacteria, commonly used as probiotic in fermented food. These microbes reduced the severity of influenza infection. The <em>Lactobacillus</em>-treated mice did not lose weight and had only mild lung damage compared with untreated mice. Similarly, others have found that treatment of mice with <em>Lactobacillus</em> protects against different <a href="https://doi.org/10.1038/srep04638" target="_blank" rel="noopener noreferrer">subtypes of</a> <a href="https://doi.org/10.1038/s41598-017-17487-8" target="_blank" rel="noopener noreferrer">influenza</a> <a href="https://doi.org/10.1371/journal.ppat.1008072" target="_blank" rel="noopener noreferrer">virus</a> and human respiratory syncytial virus – the <a href="https://doi.org/10.1038/s41598-019-39602-7" target="_blank" rel="noopener noreferrer">major cause of viral bronchiolitis and pneumonia in children</a>.</p>Chronic Disease and Microbes
<p>Patients with chronic illnesses including Type 2 diabetes, obesity and cardiovascular disease exhibit a hyperactive immune system that fails to recognize a harmless stimulus and is linked to an altered gut microbiome.</p><p>In these chronic diseases, the gut microbiome lacks bacteria that activate <a href="https://doi.org/10.1126/science.1198469" target="_blank" rel="noopener noreferrer">immune cells</a> that block the response against harmless bacteria in our guts. Such alteration of the gut microbiome is also observed in <a href="https://doi.org/10.1073/pnas.1002601107" target="_blank" rel="noopener noreferrer">babies delivered by cesarean section</a>, individuals consuming a poor <a href="https://doi.org/10.1038/nature12820" target="_blank" rel="noopener noreferrer">diet</a> and the <a href="https://doi.org/10.1038/nature11053" target="_blank" rel="noopener noreferrer">elderly</a>.</p><p>In the U.S., 117 million individuals – about half the adult population – <a href="https://health.gov/our-work/food-nutrition/2015-2020-dietary-guidelines/guidelines/" target="_blank" rel="noopener noreferrer">suffer from Type 2 diabetes, obesity, cardiovascular disease or a combination of them</a>. That suggests that half of American adults carry a faulty microbiome army.</p><p>Research in my laboratory focuses on identifying gut bacteria that are critical for creating a balanced immune system, which fights life-threatening bacterial and viral infections, while tolerating the beneficial bacteria in and on us.</p><p>Given that diet affects the diversity of bacteria in the gut, <a href="https://www.umassmed.edu/nutrition/melody-trial-info/" target="_blank" rel="noopener noreferrer">my lab studies show how diet can be used</a> as a therapy for chronic diseases. Using different foods, people can shift their gut microbiome to one that boosts a healthy immune response.</p><p>A fraction of patients infected with SARS-CoV-2, the virus that causes COVID-19 disease, develop severe complications that require hospitalization in intensive care units. What do many of those patients have in common? <a href="https://www.cdc.gov/mmwr/volumes/69/wr/mm6912e2.htm" target="_blank" rel="noopener noreferrer">Old age</a> and chronic diet-related diseases like obesity, Type 2 diabetes and cardiovascular disease.</p><p><a href="http://doi.org/10.1016/j.jada.2008.12.019" target="_blank" rel="noopener noreferrer">Black and Latinx people are disproportionately affected by obesity, Type 2 diabetes and cardiovascular disease</a>, all of which are linked to poor nutrition. Thus, it is not a coincidence that <a href="https://www.cdc.gov/mmwr/volumes/69/wr/mm6933e1.htm" target="_blank" rel="noopener noreferrer">these groups have suffered more deaths from COVID-19</a> compared with whites. This is the case not only in the U.S. but also <a href="https://www.washingtonpost.com/world/europe/blacks-in-britain-are-four-times-as-likely-to-die-of-coronavirus-as-whites-data-show/2020/05/07/2dc76710-9067-11ea-9322-a29e75effc93_story.html" target="_blank" rel="noopener noreferrer">in Britain</a>.</p>Discovering Microbes That Predict COVID-19 Severity
<p>The COVID-19 pandemic has inspired me to shift my research and explore the role of the gut microbiome in the overly aggressive immune response against SARS-CoV-2 infection.</p><p>My colleagues and I have hypothesized that critically ill SARS-CoV-2 patients with conditions like obesity, Type 2 diabetes and cardiovascular disease exhibit an altered gut microbiome that aggravates <a href="https://theconversation.com/exercise-may-help-reduce-risk-of-deadly-covid-19-complication-ards-136922" target="_blank" rel="noopener noreferrer">acute respiratory distress syndrome</a>.</p><p>Acute respiratory distress syndrome, a life-threatening lung injury, in SARS-CoV-2 patients is thought to develop from a <a href="http://doi.org/10.1016/j.cytogfr.2020.05.003" target="_blank" rel="noopener noreferrer">fatal overreaction of the immune response</a> called a <a href="https://theconversation.com/blocking-the-deadly-cytokine-storm-is-a-vital-weapon-for-treating-covid-19-137690" target="_blank" rel="noopener noreferrer">cytokine storm</a> <a href="http://doi.org/10.1016/S2213-2600(20)30216-2" target="_blank" rel="noopener noreferrer">that causes an uncontrolled flood</a> <a href="http://doi.org/10.1016/S2213-2600(20)30216-2" target="_blank" rel="noopener noreferrer">of immune cells into the lungs</a>. In these patients, their own uncontrolled inflammatory immune response, rather than the virus itself, causes the <a href="http://doi.org/10.1007/s00134-020-05991-x" target="_blank" rel="noopener noreferrer">severe lung injury and multiorgan failures</a> that lead to death.</p><p>Several studies <a href="https://doi.org/10.1016/j.trsl.2020.08.004" target="_blank" rel="noopener noreferrer">described in one recent review</a> have identified an altered gut microbiome in patients with COVID-19. However, identification of specific bacteria within the microbiome that could predict COVID-19 severity is lacking.</p><p>To address this question, my colleagues and I recruited COVID-19 hospitalized patients with severe and moderate symptoms. We collected stool and saliva samples to determine whether bacteria within the gut and oral microbiome could predict COVID-19 severity. The identification of microbiome markers that can predict the clinical outcomes of COVID-19 disease is key to help prioritize patients needing urgent treatment.</p><p><a href="https://doi.org/10.1101/2021.01.05.20249061" target="_blank" rel="noopener noreferrer">We demonstrated</a>, in a paper which has not yet been peer reviewed, that the composition of the gut microbiome is the strongest predictor of COVID-19 severity compared to patient's clinical characteristics commonly used to do so. Specifically, we identified that the presence of a bacterium in the stool – called <em>Enterococcus faecalis</em>– was a robust predictor of COVID-19 severity. Not surprisingly, <em>Enterococcus faecalis</em> has been associated with <a href="https://doi.org/10.1053/j.gastro.2011.05.035" target="_blank" rel="noopener noreferrer">chronic</a> <a href="https://doi.org/10.1016/S0002-9440(10)61172-8" target="_blank" rel="noopener noreferrer">inflammation</a>.</p><p><em>Enterococcus faecalis</em> collected from feces can be grown outside of the body in clinical laboratories. Thus, an <em>E. faecalis</em> test might be a cost-effective, rapid and relatively easy way to identify patients who are likely to require more supportive care and therapeutic interventions to improve their chances of survival.</p><p>But it is not yet clear from our research what is the contribution of the altered microbiome in the immune response to SARS-CoV-2 infection. A recent study has shown that <a href="https://doi.org/10.1101/2020.12.11.416180" target="_blank" rel="noopener noreferrer">SARS-CoV-2 infection triggers an imbalance in immune cells</a> called <a href="https://doi.org/10.1111/imr.12170" target="_blank" rel="noopener noreferrer">T regulatory cells that are critical to immune balance</a>.</p><p>Bacteria from the gut microbiome are responsible for the <a href="https://doi.org/10.7554/eLife.30916.001" target="_blank" rel="noopener noreferrer">proper activation</a> <a href="https://doi.org/10.1126/science.1198469" target="_blank" rel="noopener noreferrer">of those T-regulatory</a> <a href="https://doi.org/10.1038/nri.2016.36" target="_blank" rel="noopener noreferrer">cells</a>. Thus, researchers like me need to take repeated patient stool, saliva and blood samples over a longer time frame to learn how the altered microbiome observed in COVID-19 patients can modulate COVID-19 disease severity, perhaps by altering the development of the T-regulatory cells.</p><p>As a Latina scientist investigating interactions between diet, microbiome and immunity, I must stress the importance of better policies to improve access to healthy foods, which lead to a healthier microbiome. It is also important to design culturally sensitive dietary interventions for Black and Latinx communities. While a good-quality diet might not prevent SARS-CoV-2 infection, it can treat the underlying conditions related to its severity.</p><p><em><a href="https://theconversation.com/profiles/ana-maldonado-contreras-1152969" target="_blank">Ana Maldonado-Contreras</a> is an assistant professor of Microbiology and Physiological Systems at the University of Massachusetts Medical School.</em></p><p><em>Disclosure statement: Ana Maldonado-Contreras receives funding from The Helmsley Charitable Trust and her work has been supported by the American Gastroenterological Association. She received The Charles A. King Trust Postdoctoral Research Fellowship. She is also member of the Diversity Committee of the American Gastroenterological Association.</em></p><p><em style="">Reposted with permission from <a href="https://theconversation.com/a-healthy-microbiome-builds-a-strong-immune-system-that-could-help-defeat-covid-19-145668" target="_blank" rel="noopener noreferrer" style="">The Conversation</a>. </em></p>By Jeff Masters, Ph.D.
The New Climate War: the fight to take back our planet is the latest must-read book by leading climate change scientist and communicator Michael Mann of Penn State University.
- 12 New Books Explore Fresh Approaches to Act on Climate Change ... ›
- Dr. Michael Mann on Climate Denial: 'It's Impaired Our Ability to ... ›